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Old 28-05-2018, 04:17 PM
Startrek (Martin)
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Drift Alignment Newtonian Reflectors - Azimuth Adjustment

For the benefit of beginners like myself and others, the internet has conflicting procedures and outcomes on various websites for Drift Alignment using an illuminated reticle eyepiece ( Newtonian Reflector Telescopes )


Could experienced IIS members confirm which is correct from the two scenarios below -



Telescope pointed north and centered on alignment star near north meridian and celestial equator (Southern Hemisphere)



Scenario 1


If the star drifts North adjust azimuth on mount to the East or clockwise as you face north behind the mount
If the star drifts South adjust azimuth on mount to the West or anticlockwise as you face north behind the mount




Or


Scenario 2

If the star drifts North adjust azimuth on mount to the West or anticlockwise as you face north behind the mount
If the star drifts South adjust azimuth on mount to the East or clockwise as you face north behind the mount





Please confirm which scenario is correct ?


Thanks in advance
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Old 28-05-2018, 05:03 PM
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peter_4059 (Peter)
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Star appears to drift north because the scope is tracking south. To make it track more north to match the star's path you need to rotate the mount clockwise when viewed from above.
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Old 28-05-2018, 05:49 PM
raymo
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Don't bother with the tedious traditional drift alignment. All you need is a
DSLR. You don't have to keep looking through an eyepiece, just stand and watch your camera's screen.
Google DARV by Robert Vice. The first time will probably take you half
an hour, or even a little longer, but each time you will get quicker. You should end up doing it in 10-15mins, and it is much less tedious, and after a few goes you will get to know how accurate it needs to be for your purposes.
There is no point in aiming for perfection if your exposures are not long enough to require it. If however you are a perfectionist, you can get the accuracy to the point where you cannot improve any further owing to the periodic error in your mount's drive.
raymo
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Old 28-05-2018, 05:54 PM
Startrek (Martin)
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I forgot to mention the illuminated reticle is orientated N/S/E/W

I know there are alternative ways of PA but initially we would like to master basic drift alignment the old school way before advancing to other methods

Scenario 1 or 2 ??

Cheers
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Old 28-05-2018, 06:07 PM
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Scenario 1
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Old 28-05-2018, 07:06 PM
Startrek (Martin)
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Hi Raymo,

Thanks for your advice I’ve had quick glance at the DARV method a few months ago

It’s on my list to try after using the illuminated reticle eyepiece

I’ve been using the Skywatcher Synscan PA method on my HEQ5 for some time now and have had good results ( on a couple of occasions the PAE was Mel 000.00’00” and Maz 000.00’00” which I know is not an accurate reading) Longest exposures with this method before noticing star trailing or elongation of stars on x10 DSLR zoom was between 90 and 120 sec.

So much to learn and not enough clear night time ( patience thrown in with bit of anxiety and frustration is all part of this incredible hobby I suppose )
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Old 28-05-2018, 07:52 PM
croweater (Richard)
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Martin I used this tip from an old "Southern Astronomy" mag. Sorry if its a bit hard to read. Cheers Richard
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Old 28-05-2018, 08:24 PM
raymo
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When you say x10 DSLR zoom I presume you mean that you are using the camera and not a scope, and at 10x Live View. If that is so what length lens are you using? If its not, what exactly do you mean by 10x DSLR zoom?
raymo
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Old 29-05-2018, 07:29 AM
Startrek (Martin)
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Hi Raymo,

Apologies I should have been more specific

When I have taken an image on my 600D DSLR at prime focus on live view and review the image I magnify the image from normal to x5 and then x10 to check star trailing
The longest exposure I have achieved through the Synscan PA procedure when stars are just starting to elongate was 120sec ( Omega Centauri) but this was rare as the majority of exposures are around the 60 sec to 90 sec mark before the commencement of startrailing

Martin
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Old 29-05-2018, 10:50 AM
raymo
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I don't know what focal length scope you are using, but your max length
subs would be typical for a 1000mm f/l scope. Assuming you are using a
scope of that length, you won't get much more than 120secs with more
accurate PA, but you will of course get more consistency. I have when
experimenting achieved an occasional 150sec. Any longer than your
120secs you will have to guide.
raymo
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Old 29-05-2018, 12:57 PM
Startrek (Martin)
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Raymo,

Due to restricted exposure times my next venture is autoguiding with PHD2

Any advice on a good guide scope and camera

I was thinking about the Orion 50mm or 60mm guide scope with a ZWO AS120CM colour camera

I have a 6” f6 reflector FL 900mm on a HEQ5 mount

Thanks in advance
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Old 29-05-2018, 01:49 PM
Wavytone
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Neither. Learn to use the dec circle of the mount to align on known brights stars near the horizon (azimuth) or the meridian (altitude). This is a much faster and certain way to align. The stars themselves provide a precision alignment guide.

Drift alignment involves a lot of farnarckling in comparison.
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Old 29-05-2018, 04:38 PM
raymo
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Martin, you'd be better waiting for someone with more expertise with
guiding and guide cameras to answer your question, although I will say that an off axis guider would be superior to a guide scope because of potential problems with flexure between the main scope and the guide scope.
raymo
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